(1) Field of the Invention
The present invention relates to an LCD (liquid crystal display) device, and more specifically to a transflective LCD device.
(2) Description of the Prior Art
Due to development in the technology, multi-media products, such as mobile phones, notebook computers, digital cameras, PDAs and display screens, become more common and the demand for LCD (liquid crystal display) device is increasing day-by-day.
The LCD device can be generally classified into three types, namely: (1) transmissive (2) reflective and (3) transflective depending on supply of the light source. A backlight module is used in the transmissive LCD device and consumes a great amount of power source. Under the high ambient light (i.e. sunlight), the device has poor display ability. In the reflective type, the transmissive electrode layer is replaced by the reflective electrode layer and the device generally depends on the ambient light as the light source. Therefore, no backlight module is utilized in the reflective LCD device, but the latter suffers from non-uniform reflective brightness, thereby causing insufficient of the reflective brightness and cannot be operated under the dark environment. The transflective LCD device simultaneously has transmissive and reflective regions in order to avoid the disadvantages encountered during use of the transmissive and reflective LCD devices.
The transflective LCD structure includes an array substrate, a color filter (CF), and a liquid crystal (LC) layer. The array substrate includes a plurality of sub-pixel regions. Each sub-pixel region has a transmissive area and a reflective area. The CF has a plurality of sub-pixel regions, which are respectively aligned with the sub-pixel regions of the array substrate. The CF includes an insulating layer disposed on the reflective area of each sub-pixel region. The liquid crystal display layer is disposed between the array substrate and the color filter.
Presently, there are two transflective types. In the first type, the insulating layer is disposed on the color filter. In the second type, the insulating layer is disposed on the array substrate. The insulating layer is also called the adjustment layer since it is used to alter the thickness of the LCD layer in the reflective and transmissive areas.
Referring to FIG. 1a, a conventional transflective LCD is shown. Transflective LCD includes an array substrate 120, a color filter 110 (will be named CF later), an LC layer 130. The array substrate 120 includes a plurality of sub-pixel regions 100. Each sub-pixel region 100 has a reflective area 102 and a transmissive area 101.
The CF 110 includes a plurality of sub-pixel regions, which are respectively aligned with the sub-pixel regions 100 in the array substrate 120. Each sub-pixel region in the CF 110 has an insulating layer 140 aligned with the reflective area 102. The liquid crystal display layer 130 is disposed between the array substrate 120 and the color filter 110. An optical film 150 is further disposed on an external surface of the CF 110. Each of the sub-pixel regions 100 in the CF 110 has Red; Green and Blue colors arranged in the row manner and a plurality of the sub-pixel regions 100 cooperatively form the image on the display panel.
The array substrate 120 includes a plurality of TFTs (thin film transistor) (not shown in the drawing). The array substrate 120 further includes a reflective electrode 170 disposed on the reflective area 102 and a transmissive electrode 160 disposed on the transmissive area 101 of each of the sub-pixel regions 100. In addition, a backlight module 180 is disposed below the array substrate 120.
The external light and the backlight module 180 cooperatively supply light source to the transflective LCD panel. Flow of current through the TFTs (not numbered in the drawing) results in change of electric field between the array substrate 120 and the CF 110, thereby causing turning of the crystal molecules within the LCD layer 130, which, in turn, alters the polarization thereof such that the optical film 150 filters the different biasing light beams so as to achieve the respective brightness in each pixel. When no current is passed through the TFTs, no change is caused in the electric field such the crystal molecules within the LCD layer 130 extend vertically, thereby totally preventing passing of the light beams through the LCD layer 130.
Since the insulating layer 140 has two inclined structures at two sides; the crystal molecules thereat extend in predetermined angles, thereby forming light leakage regions 103 respectively. The light beams passing the leakage regions 103 are partially prevented and partially allowed, thereby lowing the image contrast.
Referring to FIG. 1b, another conventional transflective LCD is shown. Transflective LCD includes an array substrate 120, a CF 110, an LC layer 130 and generally similar to that of FIG. 1a. The only difference resides in that the insulating layer 140 is disposed on the reflective area 102 of the array substrate 120. This conventional transflective LCD works similar to the previous structure, and has the light leakage problem.
When using within a housing or outside of the housing, the transflective LCD panel is provided with appropriate brightness depending on the light strength of the surrounding. In case of dark state due to the light leakage in the LCD layer, the image contrast of the display panel will get lower.
Referring again to FIGS. 1a and 1b, the array substrate 120 further includes a plurality gate lines 121 and a plurality of common lines 122 generally and respectively parallel to the gate lines 121. Each common line 122 is disposed in an adjoining area between two adjacent sub-pixel regions 100 while each of the gate lines 121 is disposed between the reflective and transmissive electrodes 170, 160 of the respective sub-pixel region 100 with the reflective electrode 170 spanning across the gate line 121. A predetermined gap is defined between the reflective electrode 170 and the transmissive electrode 160 of each sub-pixel region 100 in order to prevent electrical communication therebetween.
Since no shielding is provided to cover the gap formed between the reflective and transmissive electrodes 170, 160 of the respective sub-pixel region 100, a Black Matrix 111 is provided on the CF 110 aligned with the gap so as to prevent occurrence of light leakage. According to the prior art technology, though the Black Matrix 111 can effectively prevent the light leakage between the reflective and transmissive electrodes 170, 160 of the respective sub-pixel region 100, but reduces the aperture ratio of the LCD panel.